The Plus 2s rot-prone sill strengtheners were originally made from pressed steel, but Spyder make replacements from galvanised tube and triangulated strengthening. The bodywork needs to be prised apart gently as the new sills are slotted in.

With a bit of jiggling about, you'll be able to line up the sills with the new strengthening plates, which sit on the inner sills. There are three plates on each side, each with four fixing bolts. The middle plate has the seatbelt mount.

There should be about 11 holes along the bottom of each sill (if not, mark out the new positions for the holes). Drill through the holes into the metal sill strengtheners, then fit new screws. Once done up, grind off the screw ends.

There are several bits of inner bodywork that need to be patched over, including the oval holes across the top of the rear bulkhead between the suspension towers. Grind off any old paint. You must wear a mask.

Once the paint is off, dust the areas and wipe with thinners. For big holes, prop up a sheet of aluminium to support the wet glassfibre when it's applied. In structural areas, drill into the glassfibre to help the new material bond.

Mix the glassfibre resin in a metal or glass container, because the mixture will turn some plastics brittle. Stick to the instructions - if the mixture goes off too quickly it will cause air bubbles and a lack of strength.

Work out how much glassfibre matting you will need (preferably before mixing the resin). You'll need several inches overlap. Then cut the matting with scissors and daub it with the resin, resting it on a shiny metal surface to make it easier to remove.

Lay the matting (set resin downwards) onto the area you're repairing and continue to daub it with resin, working it right into the fibres with the paint brush. Lay another three or four layers on, each one at right angles to the previous layer for strength.

As well as the rear bulkhead, there are holes in the rear suspension towers that need to be covered over. They're for the old fuel tank breathers - early cars had them at the tops of the towers, later cars had them lower, Spyder changes the breather.